1. Field of the Invention
In conventional household laundry processes for white goods such as bed linen, table linen, and white cotton goods, the articles are subjected to a combined washing and bleaching process in which the articles are treated in an aqueous bath containing an organic detergent and a bleaching (i.e., stain removing) agent. Other conventional detergent aids such as alkaline builders, for example sodium tripolyphosphate; soil suspending agents, for example sodium carboxymethyl cellulose; and optical brightening agents may also be present. The stain-removal agent is usually a "per" compound which liberates oxygen at the washing temperature. Sodium perborate is the most commonly used material for this purpose. In some instances, the stain removal may be carried out as a separate step using a compound which liberates available chlorine, such as sodium hypochlorite or N-chloro organic compounds such as dichlorocyanuric acid or its salts or trichlorocyanuric acid.
These conventional chemical processes for stain removal result in varying amounts of degradation of the textile fibers.
Dye-photoactivated oxidation reactions are known in organic chemistry, and this type of oxidation has been applied in textile bleaching processes. Very effective stain removal from textiles can be obtained by subjecting the textiles to treatment in an aqueous bath in the presence of atmospheric oxygen and certain photoactivating compounds, while at the same time irradiating the textiles with visible light, and this stain removal process can be conveniently combined with a conventional washing process.
2. Prior Art
South African No. 72-3212, an application for letters patent filed May 10, 1972, by The Procter & Gamble Company, which was laid open for public inspection on Feb. 23, 1973, and sealed on June 4, 1973, which is herein incorporated by reference, discloses a photoactivated bleaching process whereby stains are removed from textiles through the use of built detergent solutions containing sulfonated zinc phthalocyanine. These solutions are irradiated with visible light and exposed to oxygen during the washing and bleaching process. A preferred photoactivator was said to be sulfonated zinc phthalocyanine which was free from unsulfonated zinc phthalocyanine. Variation in the degree of sulfonation of zinc phthalocyanine was not found to affect the efficacy of the material as a photoactivator. It was shown to be essential that the bleach liquor contain a water-soluble alkaline detergency builder salt.
Subsequent to the South African patent application referred to above, it was demonstrated in the United States application of Thomas C. Holcombe and Robert H. Schultz, Ser. No. 419,320, filed Nov. 27, 1973, and entitled "Photoactivated Bleach--Compositions and Process", now abandoned, and the copending Divisional Application thereof, Ser. No. 611,588, filed Sept. 8, 1975 now U.S. Pat. No. 4,033,718, that the degree of sulfonation of zinc phthalocyanine does effect the efficacy of the material as a bleach photoactivator. The tri and tetra sulfonates were found to be unexpectedly effective bleach photoactivators for removing stains from textiles.
A process of bleaching textiles, especially in relation with a washing and bleaching process for household laundry, is provided by the use of photoactivated bleaches such as sulfonated zinc phthalocyanine and an alkaline builder in the presence of visible light and atmospheric oxygen. U.S. Pat. No. 3,927,967 to P. R. H. Speakman, issued Dec. 23, 1975, an entitled "Photoactivated Bleaching Process and Composition", and which is incorporated herein by reference, is directed to this process and certain compositions containing the photoactivated bleaches. This patent teaches that a builder salt is necessary, and that mere alkalinity is not effective for noticeable stain reduction on textiles. In this reference and in the two references above, the emphasis is on granular detergent compositions.
Zinc phthalocyanine was first prepared by Sir Reginald Linstead and co-workers at the Imperial College of Science and Technology of London in the 1930's, as reported in Barrett, Dent, and Linstead, "Journal of the Chemical Society", (1936) at page 1719. Then, as now, the zinc compound has tended to live in the shadow of its copper analog which is now produced in quantities of millions of pounds per year for use as pigments and dyes. The chemistry of the zinc compound is similar to that of the copper compound, in that each can be made by similar processes; each occurs in three crystalline phase structures; and each undergoes similar chemical reactions such as chlorination and sulfonation. However, the properties of the analogs are sufficiently distinct that it is mainly the copper compounds that have found commercial utilization.
Unsubstituted metal phthalocyanines are soluble in water to an unusually low degree and are used as pigments. Water solubility can be achieved to a progressively greater degree by introduction of hydrophilic groups such as sulfo, carboxy, or chloromethyl groups into the phthalocyanine molecule. This is most conveniently done by sulfonation, and up to four sulfo groups can be introduced by the use of hot oleum. Sulfonated phthalocyanines are useful as direct dyes, because they have an affinity for cellulose in the form of either cotton or paper pulp. Copper is the only metal used commercially in this way, and produces dyes that are blue to yellow-green in color, depending on the other substitutents in the molecule. A good reference work on phthalocyanine pigments and dyes is "The Chemistry of Synthetic Dyes and Pigments", edited by H. A. Lubs, Reinhold, N.Y. (1955).
The process of bleaching polymaleate polymers by irradiating them with UV light in the presence of hydrogen peroxide is known. This process is described in U.S. Pat. No. 3,496,150. Percentages and ratios given throughout the application are by weight unless otherwise indicated.